U.S. patent application number 09/893468 was filed with the patent office on 2001-12-13 for controlled release urea-formaldehyde liquid fertilizer resins with high nitrogen levels.
Invention is credited to Arthur, Lisa M., Gabrielson, Kurt D., Mirous, George E., Wertz, Stacey L..
Application Number | 20010049952 09/893468 |
Document ID | / |
Family ID | 23562114 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010049952 |
Kind Code |
A1 |
Wertz, Stacey L. ; et
al. |
December 13, 2001 |
Controlled release urea-formaldehyde liquid fertilizer resins with
high nitrogen levels
Abstract
A controlled release liquid urea formaldehyde fertilizer which
has a nitrogen level at least 31% and its method of
manufacture.
Inventors: |
Wertz, Stacey L.; (Conyers,
GA) ; Arthur, Lisa M.; (Conyers, GA) ; Mirous,
George E.; (Albany, OR) ; Gabrielson, Kurt D.;
(Lilburn, GA) |
Correspondence
Address: |
BANNER & WITCOFF
1001 G STREET N W
SUITE 1100
WASHINGTON
DC
20001
US
|
Family ID: |
23562114 |
Appl. No.: |
09/893468 |
Filed: |
June 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09893468 |
Jun 29, 2001 |
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09395212 |
Sep 14, 1999 |
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Current U.S.
Class: |
71/28 |
Current CPC
Class: |
C05G 5/20 20200201; C05C
9/02 20130101 |
Class at
Publication: |
71/28 |
International
Class: |
C05C 009/02 |
Claims
What is claimed is:
1. A urea-formaldehyde resin prepared by the method comprising: 1)
combining formaldehyde, urea, and ammonia in a basic solution at a
formaldehyde/urea/ammonia ratio of about 5.4-3.6/1/0.45-0.65; 2)
heating the solution to about 85 to about 95.degree. C., and
holding to ensure triazone formation; 3) cooling the solution to
less than about 50.degree. C., and adjusting the pH to about 9.5 to
about 10.5; 4) adding sufficient urea and ammonia to the solution
to change the ratios to about 1.1-0.6/1/0.11-0.08; 5) reheating the
solution to about 80.degree. C. to about reflux, at a pH of between
about 9 and about 11, for about 1 to about 2.5 hours; and 6) post
charging urea to bring the mole ratio to about 0.9-0.6/1/0.1-0.08;
wherein the nitrogen content of the resin is at least about 31%
based on 100% resin solids.
2. The urea-formaldehyde resin of claim 1 wherein in 1) the
formaldehyde/urea/ammonia ratio is about 5.0-4.0/1/0.5-0.6.
3. The urea-formaldehyde resin of claim 1 wherein in 1) the pH
level of the basic solution is about 7.5 to about 9.5.
4. The urea-formaldehyde resin of claim 3 wherein in 1) the pH
level of the basic solution is about 8 to about 8.6.
5. The urea-formaldehyde resin of claim 1 wherein in 2) the
temperature is about 88 to about 92.degree. C.
6. The urea-formaldehyde resin of claim 1 wherein in 2) the holding
time is about 15 to about 20 minutes.
7. The urea-formaldehyde resin of claim 1 wherein in 3) the
solution is cooled to about 35 to about 45.degree. C.
8. The urea-formaldehyde resin of claim 1 wherein in 3) the pH is
adjusted to about 9.8 to about 10.4.
9. The urea-formaldehyde resin of claim 1 wherein in 4) wherein
sufficient urea and ammonia are added to the solution to change the
ratios to about 1-0.7/1/0.1-0.09.
10. The urea-formaldehyde resin of claim 1 wherein in 5) the
solution is reheated to about 85 to about 95.degree. C.
11. The urea-formaldehyde resin of claim 1 wherein in 5) the
solution is reheated at a constant pH of between about 9.5 to about
10.5.
12. A method of producing a urea-formaldehyde resin comprising: 1)
combining formaldehyde, urea, and ammonia in a basic solution at a
formaldehyde/urea/ammonia ratio of about 5.4-3.6/1/0.45-0.65; 2)
heating the solution to about 85 to about 95.degree. C., and
holding to ensure triazone formation; 3) cooling the solution to
less than about 50.degree. C., and adjusting the pH to about 9.5 to
about 10.5; 4) adding sufficient urea and ammonia to the solution
to change the ratios to about 1.1 -0.6/1/0.11-0.08; 5) reheating
the solution to about 80.degree. C. to about reflux, at a pH of
between about 9 and about 11, for about 1 to about 2.5 hours; and
6) post charging urea to bring the mole ratio to about
0.9-0.6/1/0.1-0.08; wherein the nitrogen content of the resin is at
least about 31% based on 100% resin solids.
13. The method of claim 12 wherein in 1) the
formaldehyde/urea/ammonia ratio is 2 about 5.0-4.0/1/0.5-0.6.
14. The method of claim 12 wherein in 1) the pH level of the basic
solution is about 7.5 to about 9.5.
15. The method of claim 14 wherein in 1) the pH level of the basic
solution is about 8 to about 8.6.
16. The method of claim 12 wherein in 2) the temperature is about
88 to about 92.degree. C.
17. The method of claim 12 wherein in 2) the holding time is about
15 to about 20 minutes.
18. The method of claim 12 wherein in 3) the solution is cooled to
about 35 to about 45.degree. C.
19. The method of claim 12 wherein in 3) the pH is adjusted to
about 9.8 to about 10.4.
20. The method of claim 12 wherein in 4) wherein sufficient urea
and ammonia are added to the solution to change the ratios to about
1-0.7/1/0.1-0.09.
21. The method of claim 12 wherein in 5) the solution is reheated
to about 85 to about 95.degree. C.
22. The method of claim 12 wherein in 5) the solution is reheated
at a constant pH of between about 9.5 to about 10.5.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a controlled release liquid
urea-formaldehyde fertilizer which has a nitrogen level greater
than about 31%.
[0003] 2. Description of Related Art
[0004] Urea-formaldehyde based liquid fertilizers have been used
for some time to provide nitrogen to the soil. It is desirable that
such fertilizers be stable and provide a steady, evenly supplied,
amount of nitrogen.
[0005] In the past, long term stability of high nitrogen (around
30%) liquid urea-formaldehyde fertilizers was achieved by forming
either a high percentage (more than 30%) of cyclic triazone
structures or by condensing the urea-formaldehyde resin into small
urea-formaldehyde polymer chains.
[0006] Several patents issued to Hawkins describe the preparation
of urea-formaldehyde resins having high triazone contents. U.S.
Pat. No. 4,554,005 describes a reaction that produces at least
about 30% triazone and has a preferred urea, formaldehyde, ammonia
ratio of 1.2/1.0/0.28. U.S. Pat. No. 4,599,102 describes a reaction
that produces at least about 30% triazone and has a urea,
formaldehyde, ammonia ratio of 1.2/1.0/0.5. Both of these resins
have a high percentage of ammonia. U.S. Pat. No. 4776,879 describes
a reaction that produces at least about 75% triazone in water
insoluble forms. This material is then crystallized out and
re-dissolved at low solids levels for use. U.S. Pat. No. 4,778,510
describes a reaction that produces at least about 48% triazone.
Nitrogen release from triazone is extremely slow, therefore,
methylolated urea is preferred. The nitrogen is the useful part of
the fertilizer to the plant and thus the higher the % of nitrogen,
the more efficient the fertilizer.
[0007] Other patents describe condensing the resin into small
chains. U.S. Pat. No. 4,781,749 to Moore reacts 1.5 to 2.5 mols
formaldehyde per mole of urea in the presence of ammonium compounds
such as ammonia. This initial mole ratio is below the initial mole
ratio of 5 to 4 mols formaldehyde per mole of urea of the present
invention. The pH is maintained at near neutral conditions
(6.9-8.5) throughout the reaction. Condensed UF chains have lower
solubility than methylolated ureas and could continue to advance,
leading to extremely slow release.
[0008] U.S. Pat. No. 3,970,625 to Moore et al. describes a process
for preparing urea-formaldehyde concentrates for use as slow
release fertilizers or as adhesives. Urea and formaldehyde are
mixed in a molar ratio of 1/4.4-7.3 with no more than 0.015 wt. %
of ammonia present in the urea. The pH is adjusted to 8.8-9.5 and
the mixture is heated to 50-60.degree. C. for 30-60 minutes.
Thereafter, water is removed by distillation under reduced pressure
until solids comprise 60-90% of the remaining residue. For
producing fertilizers, the residue is heated for another 48 hours
at a temperature of 45-50.degree. C.
[0009] U.S. Pat. No. 5,449,394 to Moore relates to liquid
non-polymeric controlled-release nitrogen plant food compositions
containing the condensation products of one part ammonia, two parts
urea and three parts formaldehyde at a base buffered pH slightly
above 7. The reaction is accomplished at a temperature of about
100.degree. C. for 30-300 minutes. Water may be removed by
evaporation until the nitrogen content of the formulation is
between 20 and 30%. The solution is cooled before polymerization
producing chains of more than 3 urea moieties can occur.
[0010] It is desirable to have a method of making a stable
urea-formaldehyde resin suitable for fertilizer use that uses
significantly less triazone and no condensation, and has a higher
nitrogen concentration.
SUMMARY OF THE INVENTION
[0011] The invention describes a method of making a stable
urea-formaldehyde resin suitable for fertilizer use which uses
significantly less triazone than the Hawkins' process and no
condensation reaction like the Moore processes, has a high nitrogen
concentration, and yet is very stable, for instance, for at least
two months at 25.degree. C.
[0012] In particular, the invention is directed to a
urea-formaldehyde resin prepared by the method comprising:
[0013] 1) combining formaldehyde, urea, and ammonia in a basic
solution at a formaldehyde/urea/ammonia ratio of about
5.4-3.6/1/0.45-0.65;
[0014] 2) heating the solution to about 85 to about 95.degree. C.,
and holding to ensure triazone formation;
[0015] 3) cooling the solution to less than about 50.degree. C.,
and adjusting the pH to about 9-5 to about 10.5;
[0016] 4) adding sufficient urea and ammonia to the solution to
change the ratios to about 1.1-0.6/1/0.11-0.08;
[0017] 5) reheating the solution to about 80.degree. C. to about
reflux, at a pH of between about 9 and about 11, for about 1 to
about 2.5 hours; and
[0018] 6) post charging urea to bring the mole ratio to about
0.9-0.6/1/0.1-0.08;
[0019] wherein the nitrogen content of the resin is at least about
31% based on 100% resin solids.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention is directed to a controlled release
liquid urea formaldehyde fertilizer prepared from a solution
prepared by the reaction of formaldehyde, urea, and ammonia and
having a nitrogen level at least about 31% and a final mole ratio
of formaldehyde:urea:ammonia of about 0.9-0.6:1:0.1-0.08.
[0021] In accordance with the process of the present invention:
[0022] 1) Formaldehyde, urea, and ammonia are combined in a basic
solution at a formaldehyde/urea/ammonia ratio of about
5.4-3.6/1/0.45-0.65, preferably about 5.0-4.0/1/0.5-0.6, and most
preferably about 4.8/11.54. The pH level of the basic solution is
preferably about 7.5 to about 9.5, more preferably about 8 to about
8.6.
[0023] 2) The solution is heated to about 85 to about 95.degree.
C., preferably about 88 to about 92, and held for about 10 to about
30 minutes, preferably about 15 to about 20 minutes, to ensure
triazone formation.
[0024] 3) The solution is cooled to less than about 50.degree. C.,
preferably about 35 to about 45, and the pH is adjusted to about
9.5 to about 10.5, preferably about 9.8 to about 10.4.
[0025] 4) Sufficient urea and ammonia are added to the solution to
change the ratios to about 1.1-0.6/1/0.11-0.08, preferably about
1-0.7/1/0.1-0.09, and most preferably about 0.7/1/0.09.
[0026] 5) The solution is reheated to about 80.degree. C. to about
reflux, preferably about 85 to about 95.degree. C. at a pH of
between about 9 and about 11, preferably about 9.5 to about 10.5
for about 1 to about 2.5 hours, preferably about 2 hours.
[0027] 6) Urea is post charged to bring the mole ratio to
0.9-0.6/1/0.1-0.08.
[0028] The process of the invention provides triazone amounts of
less than about 22 weight % based on 100% resin solids.
[0029] The pH may be maintained or adjusted by adding a compound,
such as triethanolamine, borax, sodium or potassium bicarbonate, or
sodium or potassium carbonate, preferably triethanolamine, at the
start of the batch that will buffer the pH of the batch at the
desired pH level. Alternatively, the pH may be maintained by any
suitable base which is added during the reaction. While any base
can be used to increase the pH of the reaction mix, preferably
alkali metal hydroxides are used such as potassium hydroxide,
lithium hydroxide, and sodium hydroxide.
[0030] Skilled practitioners recognize that the reactants are
commercially available in many forms. Any form which can react with
the other reactants and which does not introduce extraneous
moieties deleterious to the desired reaction and reaction product
can be used in the preparation of the urea-formaldehyde resin of
the invention.
[0031] Formaldehyde is available in many forms. Paraform (solid,
polymerized formaldehyde) and formalin solutions (aqueous solutions
of formaldehyde, sometimes with methanol, in 37 percent, 44
percent, or 50 percent formaldehyde concentrations) are commonly
used forms. Formaldehyde also is available as a gas. Any of these
forms is suitable for use in the practice of the invention.
Typically, formalin solutions are preferred as the formaldehyde
source. In addition, formaldehyde may be substituted in part or in
whole with substituted aldehydes such as acetaldehyde and or
propylaldehyde. Glyxal may also be used in place of formaldehyde as
may other aldehydes not listed. It is to be recognized that the
aldehyde is dissolved (solubilized) in water or other appropriate
non-reactive organic of any desired or conventional nature, known
in the art.
[0032] Similarly, urea is available in many forms. Solid urea, such
as prill, and urea solutions, typically aqueous solutions, are
commonly available. Further, urea may be combined with another
moiety, most typically formaldehyde and urea-formaldehyde, often in
aqueous solution. Any form of urea or urea in combination with
formaldehyde is suitable for use in the practice of the invention.
Both urea prill and combined urea formaldehyde products are
preferred, such as Urea Formaldehyde Concentrate or UFC 85. These
types of products are disclosed in, for example, U.S. Pat. Nos.
5,362,842 and 5,389,716.
[0033] Commercially-available aqueous formaldehyde and
urea-containing solutions are preferred. Such solutions typically
contain between about 10 and 35 percent formaldehyde and urea.
[0034] A solution having 35% ammonia can be used providing
stability and control problems can be overcome. An aqueous solution
containing about 28 percent ammonia is particularly preferred.
Anhydrous ammonia may also be used.
[0035] In substitution in part or in whole, for the ammonia, any
primary amine or substituted primary amine may be used such as
methyl amine, monomethanol amine, amino propanol and the like.
Further, difunctional amines may be used such and ethylene diamine
or any combination of organic amines provided that one primary
amine group is available to form the triazone ring. The reaction
rates are much faster and more straight forward. Another reactant
of interest is sodium sulfamate to make the cyclic urea
sulfonate.
[0036] In a preferred embodiment of the invention, the
urea-formaldehyde liquid fertilizer resins have a free urea content
of 30-47%, a cyclic urea content of 15-22%, a monomethylol urea
content of 6-12% and a di/trimethylurea content of 25-36% based on
the urea-formaldehyde resin and, based on a 60-70% urea solution, a
free urea content of 20-31%, a cyclic urea content of 9.9-14.5%, a
monomethylol urea content of 4-8% and a di/trimethylurea content of
16-23% wherein the rest of the solution is composed of water,
ammonia, and formaldehyde.
[0037] The urea-formaldehyde liquid resin of the invention may then
be used as a fertilizer. Other additives may be mixed into the
liquid fertilizer prior to use such as any of a wide variety of
well-known inorganic fertilizer nutrients based on phosphorous and
potassium. Pesticides may also be mixed in, e.g., to control weeds
and kill insect larvae. Suitable additives are within the skill of
the art.
[0038] The following examples are for purposes of illustration and
are not intended to limit the scope of the claimed invention.
EXAMPLES
Example 1
[0039] Urea and formaldehyde were reacted in the presence of 1.6%
ammonia to produce a product having a pH above 7 and containing
urea-formaldehyde in a mole ratio of 0.64 (F/U).
1 Conc. % Weight % Moles UFC 85 85 35.3 Formaldehyde (from UFC) 100
21.2 .71 Urea (from UFC) 100 8.8 .15 Ammonia 28 4.8 .08 Urea 100
57.1 .95 Ammonia 28 1.0 .02
[0040]
2 Mole Ratio U/F 1.6 F/U 0.6 F/A 7.4 U/A 11.5
[0041] NMR results indicated that the resin has a cyclic urea
(triazone) concentration of 16.9% based on 100% resin solids.
[0042] The results are compared with the patents issued to
Hawkins:
3 U.S. Pat. No. % Triazone U/F/A Ratio 4,554,005 >30
1.6/1.0/0.28 4,599,102 >30 1.2/1.0/0.5 4,776,879 >75
4,778,510 48
[0043] The Hawkins patents have a high percentage of ammonia and a
high triazone content which contains very slow nitrogen
release.
Example 2
[0044] A urea-formaldehyde resin was prepared in accordance with
the present invention in a three stage reaction and then compared
with a resin prepared in accordance with Moore, U.S. Pat. No.
4,781,749.
[0045] Stage 1
4 Invention Moore (comparative) U:F mole ratio .21 0.4-0.67 pH
8.0-8.6 6.9-8.5 Buffer Triethanolamine Sodium Bicarbonate
[0046] Stage 2
5 Invention Moore (comparative) U:F mole ratio 1.42 1.0-1.7
(1.3-1.5) pH 9.8-10.4 6.9-8.5 Buffer pH maintained w/NaOH Sodium
Bicarbonate
[0047] Stage 3
6 Invention Moore (comparative) U:F mole ratio 1.56 No stage 3 pH
9.0-9.5 Buffer pH maintained w/NaOH
[0048] The Moore patent describes a polymethylene urea fertilizer
solution which is condensed at a neutral pH into small water
soluble chains. Free urea and DMU are minimized due to the polymer
formation and the high:formaldehyde mole ratio which allows Moore
to get good long term stability on his solution. (28-0-0)
solution.
[0049] The inventive resin was synthesized at high pH to eliminate
the possibility of condensation and thus does not contain water
soluble chains. The initial mole ratio differences also leads to a
higher possibility of DMU, MMU, etc. formation. The inventive resin
has a large amount of free urea in the solution which is soluble in
the triazone formed early in the synthesis. The inventive resin
also has a urea post-add to boost nitrogen concentration. (31.5-0-0
solution).
Example 3
[0050] Several liquid fertilizer solutions were tested including
the commercial resin Nitro 30. The test results are shown in the
table below.
7 Nitro 30 Inventive 1 Inventive 2 Nitrogen Conc. 29.1 31.4 31.7
Free Urea 53 45 43 Storage Stability 2 months+ 2 months+ 2 months+
Triazone Conc. 11% 16% 12% F/U Mole Ratio 0.55 0.64 0.64
[0051] The nitrogen concentration was significantly higher for the
Inventive 1 and Inventive 2 than Nitro 30. The free urea of
Inventive 1 and Inventive 2 were lower than Nitro 30 which leads to
more slow release nitrogen.
[0052] It should be understood that while the invention has been
described in conjunction with specific embodiments thereof, the
foregoing description and examples are intended to illustrate, but
not limit the scope of the invention. Other aspects, advantages and
modifications will be apparent to those skilled in the art to which
the invention pertains, and these aspects and modifications are
within the scope of the invention, which is limited only by the
appended claims.
* * * * *